RESUMO
The use of pore forming agents and plasticizers are efficient ways to obtain membranes for controlled drug permeation through polymeric membranes. The challenge of the present study was to combine these two strategies to obtain cellulose acetate (CA) membranes, where poly(caprolactone triol) (PCL-T) was used as a plasticizer and water, dissolved in a casting solution, was used as a pore forming agent. First, the influence of water on membrane morphology, porosity and the permeation coefficient of a model drug (paracetamol) was analyzed. The influence of different amounts of PCL-T on the permeation coefficient of the CA membranes was then evaluated. Finally, both strategies were combined to obtain porous CA/PCL-T membranes. The membrane microstructure was analyzed using scanning electron microscopy (SEM), the CA crystallinity was determined via differential scanning calorimetry (DSC), and membrane permeability was investigated using paracetamol. The addition of water, a non-solvent, during the membrane casting process was found to be a simple and effective way to change membrane porosity and consequently the drug-permeation profile. When small quantities of non-solvent were used to obtain low porosity membranes, the presence of a plasticizer agent could be used to better modulate drug permeation. Combining the addition of PCL-T with the use of a non-solvent resulted in a series of CA membranes with paracetamol-permeation coefficient values in the range of ca. 10(-7) to 10(-5) cm s(-1).
Assuntos
Celulose/análogos & derivados , Celulose/farmacocinética , Filtros Microporos/normas , Plastificantes/farmacocinética , Celulose/química , Permeabilidade/efeitos dos fármacos , Plastificantes/química , Água/química , Água/metabolismoRESUMO
Four soil fungi able to grow under low oxygenation conditions were selected and used in studies to determine the production of enzymes that promote the degradation of lignocellulosic materials. The capacity of these fungi to ferment such materials was also investigated. The fungi were grown in sugarcane bagasse and sawdust at final concentrations of 4 and 10%, as the carbon sources. The strains were cultivated under microaerophilic and combined conditions of oxygenation (aerobic followed by microaerophilic conditions). The results obtained with the basidiomycete specie, Trichocladium canadense, Geotrichum sp., and Fusarium sp. suggest that they prefer lower oxygen concentration for growth and enzyme production. Lignocellulolytic activities were detected in all strains but varied with the carbon source used. The highest levels of these activities were produced by the Basidiomycete specie and Fusarium sp. Ethanol and other nongaseous fermentation products were detected following high-performance liquid chromatography analysis using a supelcogel C-610H column, demonstrating the fermentative capability of these strains. In view of their ability to produce enzymes necessary for the breakdown of lignocellulosic materials and to utilize most of the degradation products for growth, these strains have a great potential for biotechnological application.
Assuntos
Celulose/farmacocinética , Fungos/crescimento & desenvolvimento , Fusarium/crescimento & desenvolvimento , Geotrichum/crescimento & desenvolvimento , Glicosídeo Hidrolases/metabolismo , Lignina/farmacocinética , Biomassa , Meios de Cultura , Fermentação , Fungos/enzimologia , Fusarium/enzimologia , Geotrichum/enzimologia , Cinética , Consumo de Oxigênio , Especificidade por SubstratoRESUMO
Microcrystalline cellulose (MCC) is a very important product in pharmaceutic, food, cosmetic and other industries. In this work, MCC was prepared from soybean husk, produced in large quantities in soybean oil processing industries. It was characterized through various techniques (scanning electron microscopy (SEM), infrared spectroscopy (FTIR), thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC)) and compared with a commercial MCC. The results obtained show that the prepared sample has similar crystallinity and lower particle size than the commercial MCC. Both MCC samples were treated with organic solvents (chloroform, acetone, ethanol and ethyl ether), for structural modifications to be introduced, and used as acetylsalicylic acid (ASA) carrier. Pretreated MCC and MCC/ASA 1:1 mixtures were analyzed through FTIR and thermal analysis. The drug release was evaluated in buffer solution of pH 4.5 and in pure water, at 37 degrees C. The MCC pretreated with different solvents show different thermal properties and ASA release rates, each MCC showing a particular behavior.
Assuntos
Anti-Inflamatórios não Esteroides/farmacocinética , Aspirina/farmacocinética , Celulose/química , Excipientes/química , Solventes/química , Celulose/farmacocinética , Portadores de Fármacos , Excipientes/farmacocinética , Glycine max/químicaRESUMO
Os efeitos hemostáticos da celulose oxidada (Surgicel) sao bem conhecidos. Baseados na similaridade estrutural e em um possível efeito hemostático, estudamos a esponja de celulose liofilizada utilizando dois modelos experimentais. Fase I - Realizada em 12 caes, consistiu na provocaçao de lesao cortical com sangramento, introduçao de fragmento de esponja de celulose liofilizada no interior da lesao e medida do tempo necessário para obter-se hemostasia. Os animais foram sacrificados em 7, 30 e 90 dias. A hemostasia foi obtida, em média, após 1 minuto e nenhum efeito colateral clínico foi detectado. A microscopia mostrou reaçao histiocitária leve aos 7 e 30 dias, com presença de pequena quantidade de células gigantes tipo corpo estranho. A reaçao histioplasmocitária regrediu e, aos 90 dias, a celulose estava circundada por pobre reaçao inflamatória. A membrana liofilizada revelou ter aspecto peculiar, representado por filamentos eosinofílicos, circundados por reaçao inflamatória, que diminuiu com o tempo. Somente esparsos e irregulares filamenos eosinofílicos foram percebidos aos 90 dias. Fase II - Foram introduzidos fragmentos de dimensoes conhecidas de esponja de celulose, no interior do fígado de 12 ratos, que foram sacrificados em 7, 30 e 90 dias. Na autopsia, a inspeçao a olho desarmado constatou, aos 30 e 90 dias, a formaçao de bridas peritoneais na altura do implante. Em todos os animais, especialmente aos 7 dias, a microscopia revelou intensa reaçao histiolinfoplasmocitária ao redor do implante. Em dois animais, aos 90 dias, detectaram-se grânulos refringentes à luz polarizada, no interior de células gigantes, demonstrando fagocitose ativa de celulose. Em conclusao, observou-se haver necessidade de modelo experimental comparativo para provar a existência de propriedades hemostáticas na esponja. Conseguiu-se, no entanto, provar a existência de reabsorçao da celulose em mamíferos através de fagocitose, fato este ainda nao relatado na literatura.